I agree, it is semantics, but that's what definitions are. Intimate has different meanings, including "closely acquainted; familiar..." And to me it really makes the definition overly broad and not helpful.

But I see, you have a clear opinion that it is cheating. I don't think it is that clear-cut.
For me personally the biggest concerns are: a) I could catch a disease and somehow pass it on to my spouse. b) I am spending my money, but I could put it into a pension fund instead, so I funnel funds away.

What I mean is that "cheating or not" is much more a question of the individual circumstances than a random definition pulled from the web. My criteria in the end are whether I do harm to the relationship with my spouse. I understand that this is not synonym to cheating, but a more helpful question than getting a black-or-white yes or no to the question of whether it cheating.